Our study of the glycobiology of human medulloblastoma seeks to identify potentially biologically active glycosphingolipid molecules in human medulloblastoma, to define their molecular structures, to elucidate their metabolism including shedding into the cerebrospinal fluid, and ultimately to alter this process with the aim of abrogating shedding of tumor-derived immunosuppressive molecules. We have fully analyzed the glycosphingolipid composition of the DAOY cell line, a representative human medulloblastoma cell line, and have elucidated the structure of the individual ganglioside molecules by fast atom bombardment mass spectrometry and FAB-MS/MS. These studies demonstrate a marked heterogeneity of ceramide structure is a characteristic of human tumors which may be more prevalent than previously appreciated. Most recently, we have conducted similar studies, using FAB-MS and FAB-MS/MS, to characterize the gangliosides of medulloblastoma tumor biopsies. It is highly likely that these latter studies will lead to identification of specific gangliosides as potential markers of these tumors, by shedding into the cerebrospinal fluid.